1. Field of the Invention
This invention relates to an external combustion engine for outputting mechanical energy by converting the displacement of a working liquid caused by the volume change of the vapor thereof into the mechanical energy.
2. Description of the Related Art
One of the conventional external combustion engines disclosed by Japanese Unexamined Patent Publication No. 205-330910 is adapted so that a working liquid is sealed in a container and part of the working liquid is heated and vaporized in a heated portion while the vapor of the vaporized working liquid is liquefied by being cooled in a cooled portion, thereby outputting by converting, to mechanical energy, the displacement of the working liquid caused by the volume change of the vapor thereof.
In this conventional technique, the external combustion engine includes a pressure sensor for detecting the internal pressure of the container, a temperature sensor for detecting the temperature of the heated portion of the container for vaporizing the working liquid, a valve for discharging the working liquid from the container into the atmosphere and a control unit for controlling the on/off operation of the valve.
In the case where the internal pressure of the container exceeds the saturation vapor pressure of the working liquid at the temperature of the heated portion, part of the working liquid in the container is discharged into the atmosphere and the volume of the working liquid is reduced thereby to control the internal pressure of the container not to exceed the saturation vapor pressure of the working liquid.
As a result, the internal pressure of the container is prevented from exceeding the saturation vapor pressure of the working liquid and part of the vapor from being condensed and liquefied, thereby suppressing a reduction in the output and efficiency of the external combustion engine (see FIG. 3C as described later).